The present invention relates generally to line voltage regulation and, more particularly, to line voltage regulation suitable for providing wide voltage range control for an electric resistance heater, for example, such as in electrical cooking apparatus.
The most common approach to temperature control for cooking apparatus is to use a closed-loop control wherein the temperature of the heating element is determined using a sensor, and an automatic control is used to adjust the power to the heating element in order to reach and maintain the desired temperature. A thermostat may be used for this purpose. Although closed-loop temperature control is effective, it is not easy or practicable for some applications.
In apparatus employing resistive heating elements powered by an external source of electric power, it is desirable to regulate the energy dissipated in the heating element against variations in voltage. For a heating element with a fixed resistance, the power dissipated in the element is proportional to the voltage-squared such that small changes in source voltage can result in large changes in element power. For some applications, such as cooking appliances, for example, such variations can result in performance degradation.
Accordingly, it is desirable to provide line voltage regulation (or compensation) such that an effectively constant power is provided to a heating element, for example, even though the line voltage is varying. It is furthermore desirable that such line voltage compensation for heating apparatus would enable operation over a wide voltage range or even in systems with different nominal voltages.